[1] Univ Hosp Maastricht, Maastricht, Netherlands
[2] Univ Oxford Wolfson Coll, Oxford OX2 6UD, England
[3] Univ Oxford, Oxford, England
[4] Univ York, Centre Reviews & Dissemination, York YO10 5DD, N Yorkshire, England
[5] Univ Dundee, Dundee, Scotland
[6] Cochrane Collaboration, Rome, Italy
[7] Univ Hosp Maastricht, MAASTRO GROW, Maastricht, Netherlands
[8] Univ Oxford, Univ Oxford Wolfson Coll, Oxford, England
[9] Univ York, Ctr Reviews & Disseminat, York, N Yorkshire, England
[10] Cochrane Collaboration, Rome, Italy